Androgen receptor function and androgen receptor–targeted therapies in breast cancer: A review

IMPORTANCE: The androgen receptor (AR) pathway is emerging as a potential therapeutic target in breast cancer. To date, AR-targeted drugs have been approved only for treatment of prostate cancer; however, AR-targeted treatment for breast cancer is an area of active investigation. Through review of preclinical studies, retrospective clinical studies, and clinical trials, we examined the biology of AR and AR-related pathways, the potential for AR-targeted therapies in breast cancer, and potential biomarkers for AR-targeted treatments. OBSERVATIONS: The rate of AR positivity in breast cancer is about 60% to 80%. Biologically, the AR pathway has cross-talk with several other key signaling pathways, including the PI3K/Akt/mTOR and MAPK pathways, and with other receptors, including estrogen receptor and human epidermal growth factor receptor-2. The value of AR positivity as a prognostic marker has not yet been defined. Androgen receptor–targeted therapies, including AR agonists, AR antagonists, and PI3K inhibitors, have shown promising results in clinical trials in patients with breast cancer, and combinations of AR-targeted therapies with other agents have been investigated for overcoming resistance to AR-targeted therapies. Biomarkers to stratify patients according to the likelihood of response to AR-targeted drugs are yet to be established. Potential biomarkers of response to AR inhibitors include AR phosphorylation and AR gene expression. CONCLUSIONS AND RELEVANCE: Androgen receptor–targeted treatments for breast cancer are in development and have shown promising preliminary results. In-depth understanding of AR and AR-related signaling pathways would improve the treatment strategies for AR-positive breast cancer. Further preclinical and clinical studies of AR-targeted drugs alone and in combination with other drugs are justified and warranted to clarify the biology of AR and inform the development of AR-targeted therapies to improve survival outcome in patients with breast cancer.